Owner vs Organization Adminstrator vs Billing Account Adminstrator

I am lost in GCP role-land. I see two very similar looking roles:

Owner - Full access to all resources

Organization Administrator - Access to administer all resources belonging to an organization

Even with both roles, I still couldn't access the billing accounts I hadn't personally created. So then I discovered a third permission that let me see those:

Billing Account Administrator - Authorized to see and manage all aspects of billing accounts.

1. What are the differences between these three?

2. When should I use them?

3. Is there a "superuser" role that allows me to do all the things?

Unfortunately there isn't a "super user" role that will allow you to do all the things in GCP.

Owner is indirectly the super user role because with Owner role you can give yourself all the other permissions/roles that you need.

You can create a custom role (say superuser) and add all GCP permissions into the role and assign it yourself, but this becomes a mundane task. This comes with a limitation of 64 KB max role size and is left for experimentation.

Note: Organization level and project level roles are different, and owner of a project doesn't mean owner of an organization.